A liquid crystal display (LCD) differs from an organic light emitting displays (OLED) in that, a liquid crystal display does not emit light itself, and a backlight is usually provided by a backlight module to the liquid crystal display, so as to achieve display. The backlight modules are classified into direct-type backlight module and edge-type backlight module according to positions of a light source and a display panel. The light source of the direct-type backlight module is located directly below the display panel, and the light source of the edge-type backlight module is located at one side of the display panel. But no matter for direct-type backlight module or edge-type backlight module, in view of the fact that liquid crystal panel serve for planar displaying, and then all of existing backlight modules are backlight sources with planar luminescence, they cannot satisfy requirements of a special display, such as, ring display.